Flexible polyurethane foam



United States Patent 3,280,055 FLEXIBLE POLYURETHANE FOAM Billy DonDavis, Lake Jackson, Tex., assignor to The Dow Chemical Company,Midland, Mich., a corporation of Delaware N0 Drawing. Originalapplication Sept. 1, 1960, Ser. No. 53,338, now Patent No. 3,207,710,dated Sept. 21, 1965. Divided and this application July 26, 1965, Ser.No. 474,954

4 Claims. (Cl. 26019) This application is a division of my copendingapplication Serial No. 53,338, filed September 1, 1960, now issued asPatent No. 3,207,710.

This invention relates to flexible polyurethane foams and to methods forthe production of such foams.

According to the invention flexible foams having high energy-absorbingpower, and hence suitable for use in crash pads and the like, are madeby the reaction of an .arylene diisocyanate with a polyol compositionmade by 1) condensing a phenol-aldehyde resin containing an average ofabout -16 phenol aldehyde units per molecule with about 20-50 moles ofan alkylene oxide per phenol unit in the resin, (2) esterifying allexcept 2 to 3 of the hydroxyl groups in the oxyalkylated resin with alongchain fatty acid and (3) heating the resulting ester with about 0.5to 2 parts by weight, based on ester, of a long-chain aliphaticpolyoxyalkylene triol until the acid number of the product is less thanabout 2.5, and preferably less than 1.5. The ratio of diisocyanate topolyol should be such as to provide about l-2 isocyanate groups perhydroxyl group.

Any normally liquid aromatic diisocyanate may be used. Suitable onesinclude benzene diisocyanate, tolylene diisocyanates, and the like.

In order to obtain the desired flexibility in the polyurethane foam itis essential that the diisocyanate and the polyol be reacted and theproduct foamed in a single step; i.e., by the one-shot technique ratherthan by the pre polymer technique. For this purpose the polyol is mixedwith conventional catalysts, surfactants, blowing agents, foamregulators, etc. after which the resulting mixture is blended with allthe diisocyanate in a single step, whereupon the polymer simultaneouslyforms and foams. The product is then cured conventionally; for example,by being heated at about 50-100 C. in an oven for about 1 hour.

The foams made by the process of the invention are characterized bytheir flexibility and high energy-absorbing power. These properties makethem espectially suitable for padding safety helmets and automobile.dashboards, as packaging material for fragile objects and in similaruses where their shock-absorbing properties are useful.

The practice of the invention is illustrated by the following example.

One mole of a phenol-formaldehyde resin containing an average of 8phenol groups per molecule was condensed with propylene oxide in thepresence of alkali catalyst until 35 moles of oxide per phenolic grouphad been consumed. The product was then condensed with 4 moles ofethylene oxide per phenolic group. Three hundred grams of theoxyalkylated phenol-form-aldehyde resin thus obtained was heated at 265C. for 14.5 hours with 264 g. of tall oil fatty acids, water beingcontinuously 3,280,055 Patented Oct. 18, 1966 removed azeotropically bya few ml. of xylene included in the reaction mixture. When the reactionwas stopped the xylene was distilled out under vacuum. The polyesterresin thus obtained had a viscosity of more than 1000 stokes and an acidnumber of 2.3.

Equal parts, by weight, of the above polyester resin and polyglycol11-80 were mixed and heated at 245 C. for 2 hours, to produce a polyolproduct having a viscosity of 360 stokes and an acid number of 1.08.Polyglycol 11-80 is a product formed by condensing propylene oxide withglycerol and having a viscosity of 80 centistokes at 100 F. andmolecular Weight of 650.

Polyurethane foam was made form the above polyol composition by use ofwater as the blowing agent and with conventional amine catalysts and aconventional surfactant or dispersing agent as follows:

To g. of polyol was added 1.4 g. of water, 1.0 g. of N-coco-morpholine,0.25 g. of triethylenediamine and 0.06 g. of Tween 20 (a polyoxyethylenesorbitan monolaurate). After these ingredients had been thoroughly mixedthere was added 24.5 g. of tolylene diisocyanate (:20 ratio of 2,4 and2,6 isomers). This was rapidly mixed for 30 seconds and discharged intoa mold. The resulting foam was cured in an oven at 70 C. for 1 hour. Ithad a density of 3.5 lb. per cubic foot; compression set, 7.0%; tensilestrength, 13 p.s.i.; and hysteresis, 84%. After being aged 3 hours at220 F. and humidity its compression set was 24% and hysteresis was 94%.It was soft and flexible and had a small, uniform cell structure.

Foamed resins having the valuable properties of that described above arealso obtained by substituting equivalent materials and procedures forthose used in the above example. Thus, for example, the phenol-aldehyderesin may be made from an alkylphenol or another aliphatic monoaldehydeor it may contain as few as 5 or as many as 16 phenolic units. Inoxyalkylating the resin, from about 20 to 50 moles of oxide per phenolicunit may be used and it may be ethylene oxide, propylene oxide or amixture of the two. Instead of tall oil fatty acids I can use other longchain fatty acids, such as oleic, linoleic, stearic, palmitic, lauric ormixtures of such acids. Instead of polyglycol 11-80 I can use anyaliphatic long-chain triol having a molecular weight of about 400-800.Instead of polyglycols, for example, I can use castor oil. In making thefoam other conventional blowing agents, catalysts, surfactants, etc. maybe used.

I claim:

1. An aliphatic polyol composition made by (1) condensing aphenol-aldehyde resin containing 5 to 16 phenol units per molecule withabout 20 to 50 moles of alkylene oxide wherein the alkylene radicalseach contain two to three carbon atoms, thus to form an oxyalkylatedphenolaldehyde resin (2) esterifying all except 2 to 3 of the hydroxylgroups per molecule in said resin with a longchain fatty acid; and (3)mixing and, if necessary, heating the partially esterified resin withabout 0.5 to 2 parts by weight of a long-chain aliphatic triol having amoleculare weight of about 400 to 800, said heating being sufficient toresult in the product having an acid number of not more than 2.5.

2. A polyol composition as defined in claim 1 wherein thephenol-aldehyde resin is made from phenol and formaldehyde.

3. A polyol composition as defined in claim 2 wherein 3 4 the aliphatictriol is that obtained by the oxyalkylation 2,620,319 12/1952 Rowe260-19 of glycerol by condensation with an alkylene oxide in 2,863,85412/ 1958 Wilson 260-75 which each alkylene radical contains two to threecar- 2,863,855 12/ 1958 Wilson 26075 bon atoms. 2,967,838 1/ 1961Partansky 26019 4. A polyol composition as defined in claim 3 wherein 5the fatty acid is tall oil fatty acids. FOREIGN-PATENTS 5 42 ReferencesCited by the Examiner 38 6 3/1957 Canada UNIT D STATES PA LEON IBERCOVITZ, Primary Examiner. 2,542,008 2/1951 De Groote 260-19 10 F.MCKELVEY, Assistant Examiner.

1. AN ALIPHATIC POLYOL COMPOSITION MADE BY (1) CONDENSING APHENOL-ALDEHYDE RESIN CONTAINING 5 TO 16 PHENOL UNITS PER MOLECULE WITHABOUT 20 TO 50 MOLES OF ALKYLENE OXIDE WHEREIN THE ALKYLENE RADICALSEACH CONTAIN TWO TO THREE-CARBON ATOMS, THUS TO FORM AN OXYALKYLATEDPHENOLALDEHYDE RESIN (2) ESTERIFYING ALL EXCEPT 2 TO 3 OF THE HYDROXYLGROUPS PER MOLECULE IN SAID RESIN WITH A LONGCHAIN FATTY ACID; AND (3)MIXING AND IF NECESSARY HEATING THE PARTIALLY ESTERIFIED RESIN WITHABOUT 0.5 TO 2 PARTS BY WEIGHT OF A LONG-CHAIN ALIPHATIC TRIOL HAVING AMOLECULARE WEIGHT OF ABOUT 400 TO 800, SAID HEATING BEING SUFFICIENT TORESULT IN THE PRODUCT HAVING AN ACID NUMBER OF NOT MORE THAN 2.5.